#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<vector>
#include<map>
#include<queue>
#include<string>
#include<sstream>
#include<cmath>
#include<numeric>
using namespace std;

int main(){

  int n, m;
  cin >> n >> m;
  vector<int> a(m);
  for(int i=0; i<m; i++) cin >> a[i];
  vector<int> card(n+1, 0);
  for(int i=0; i<n+1; i++) card[i] = i;

  for(int i=0; i<m; i++){
    card[0] = card[ a[i] ];
    for(int j=a[i]-1; j>=0; j--){
      card[j+1] = card[j];
    }
  }
  cout << card[0] << endl;



  return 0;
}